Head masters have launched a bitter attack on the Government’s “deeply flawed”
league tables after a string of top private schools were named last on a
technicality.

Almost 150 fee-paying schools dropped to the bottom of rankings published on Wednesday after pupils sat "tougher" International GCSEs.

Many schools, including Eton, Rugby, Dulwich, Sevenoaks and St Paul’s, shun conventional courses in subjects such as English, maths and science which they claim lack academic rigour.

But the Government still refuses to recognise the IGCSE because it fails to precisely follow the National Curriculum.

It means dozens of England’s most highly regarded schools officially register “zero” on the Government’s basic measure of a decent education – the number of pupils gaining five A* to C grades, including English and maths.

Dr Martin Stephen, High Master of St Paul's boys' school in West London, said the tables were "clearly a lie".

"You need to ask how can we be the highest performing school in the country by every measure except by the government one?" he said.

Gillian Low, president of the Girls’ Schools Association and headmistress of Lady Eleanor Holles School, Hampton, said: “The league tables are completely undermined by this failure to recognise a good qualification. How can a qualification recognised by some of the most academic schools in the country be deemed unworthy just because it doesn’t tick all the National Curriculum boxes?”

In total, 145 private schools notched up zero scores in the Government's attainment measures. It is thought this was just due to IGCSEs – particularly in English and maths – being excluded.

Last year, ministers announced that they would allow IGCSEs in non-compulsory GCSE subjects such as history to be formally accredited. But it insisted that qualifications in the core subjects of English, maths and science would not be counted.

The Conservatives have pledged to allow all schools to take the IGCSE – paving the way for its inclusion in the official rankings.

David Lyscom, chief executive of the Independent Schools Council, said: "The comparison of school performance via league tables is deeply flawed, in particular given the wide variety of valid qualifications currently on offer, and the differing views of their worth.”

But a spokesman for the Department for Children, Schools and Families said: "This is a fatuous argument. The IGCSE does not meet the requirements of the National Curriculum and so it is not approved for use in curriculum in state schools - it would make absolutely no sense for it to be included in the end-of-year tables just because some independent schools choose to offer them."